coochy coo
/ˌkuːtʃi ˈkuː/(also coochie coo, koochie coo, koochie koo)
exclamation
Used to elicit a smile or laughter from a baby, especially in combination with tickling.
Origin
Late 19th century; earliest use found in The Oakland Tribune. Origin uncertain; perhaps imitative of a baby's gurgling; perhaps compare coo.